a. Field of the Invention
The present invention relates to a communication terminal for use in a communication or video conferencing system.
b. Related Art
Video conferencing systems facilitate interactive collaborative working between individuals at different locations using computers as a communication tool. Within conventional video conferencing systems, the users may have separate data and audio links. Data relating to the application upon which the users are collaboratively working in conjunction with visual data, representing the images of the parties, are exchanged via a packet based data network. The audio and data links are conventionally established using a telephone network and packet based data network respectively.
The interactions involved during collaborative working may relate to, for example, discussing the financial planning aspects of a project; for which the parties have a financial model and manipulate using, say, a spread sheet on a chalk board in the conventional manner. Each party would have a copy of the relevant financial model on the screen of their communication terminal or video conferencing terminal. However, only one party will have total control over the operation of the model, that is, only one party will be able to effect changes to the model. Discussions and interactions take place using the data and audio links. An addressor draws the attention of an addressee to a particular aspect of the model using a pointer controlled by, say, a mouse or other suitable input device.
The pointers of both parties are displayed on both terminal screens simultaneously. The simultaneous display of the pointers on the screens of both parties is effected by exchanging pointer location co-ordinates over the packet based data network. The packet based data network can be either switched or non-switched. In order that the parties to the conference perceive the system as being real-time and as having an interactive feeling the pointer location co-ordinates need to be exchanged approximately fifteen to twenty-five times per second.
The exchange of co-ordinates in existing systems is also usually effected via the packet based data network. This is to be contrasted with the exchange of audio information via a telephone network. Referring to the latter, the communication is almost instantaneous whereas with the former there is invariably an end-to-end delay or network latency. Consequently, a scenario can be envisaged in which an addressor attempts to draw the attention of an addressee to a particular aspect of the model using their pointer while simultaneously articulating "Look at this" and, due to network latency, the new pointer co-ordinates corresponding to current pointer location of the addressor's terminal at the time of the articulation will not have reached the addressee's terminal. This will have the effect of drawing the addressee's attention to whatever aspect of the model the addressor's old pointer location co-ordinates were indicating thereby introducing scope for misunderstanding between the parties.